Department of Materials Science and Engineering, The Kroto Research Institute, The University of Sheffield, North Campus, Broad Lane, Sheffield, S3 7HQ, UK,
J Mater Sci Mater Med. 2014 Feb;25(2):527-53. doi: 10.1007/s10856-013-5067-2. Epub 2013 Oct 20.
Oesophageal cancer is the ninth leading cause of malignant cancer death and its prognosis remains poor, ranking as the sixth most frequent cause of death in the world. This research work aims to adopt an Auxetic (rotating-squares) geometry device, that had previously been examined theoretically and analysed by Grima and Evans (J Mater Sci Lett 19(17):1563-1565, 2000), to produce a novel Auxetic oesophageal stent and stent-grafts relevant to the palliative treatment of oesophageal cancer and also for the prevention of dysphagia. This paper discusses the manufacture of a small diameter Auxetic oesophageal stent and stent-graft. The oral deployment of such an Auxetic stent would be simplest if a commercial balloon dilatational catheter was used as this obviates the need for an expensive dedicated delivery system. A novel manufacturing route was employed in this research to develop both Auxetic films and Auxetic oesophageal stents, which ranged from conventional subtractive techniques to a new additive manufacturing method. Polyurethane was selected as a material for the fabrication of Auxetic films and Auxetic oesophageal stents because of its good biocompatibility and non-toxicological properties. The Auxetic films were later used for the fabrication of seamed Auxetic oesophageal stents. The flexible polyurethane tubular grafts were also attached to the inner luminal side of the seamless Auxetic oesophageal stents, in order to prevent tumour in-growth. Scanning electron microscopy was used to conduct surface morphology study by using different Auxetic specimens developed from different conventional and new additive manufacturing techniques. Tensile testing of the Auxetic films was performed to characterise their mechanical properties. The stent expansion tests of the Auxetic stents were done to analyse the longitudinal extension and radial expansion of the Auxetic stent at a range of radial pressures applied by the balloon catheter, and to also identify the pressure values where the Auxetic stent fails. Finite element models of both Auxetic film and Auxetic stent were developed, and the results were compared with experimental results with a good agreement. The tensile testing of the Auxetic polyurethane films revealed that the Poisson's ratio of the sample ranged between -0.87 and -0.963 at different uniaxial tensile load values. From the stent expansion test, it was found that the Auxetic oesophageal stent radially expanded from 0.5 to 5.73 mm and longitudinally extended from 0.15 to 1.83 mm at a range of applied pressure increments (0.5-2.7 bar) from the balloon catheter.
食管癌是恶性癌症死亡的第九大主要原因，其预后仍然较差，是世界上第六大最常见的死亡原因。本研究工作旨在采用先前经过理论研究的 Grima 和 Evans 分析过的（Grima 和 Evans，J Mater Sci Lett 19（17）：1563-1565，2000）的（Auxetic（旋转正方形））几何装置，产生一种新型的（Auxetic）食管支架和支架移植物，以用于食管癌的姑息治疗，并预防吞咽困难。本文讨论了一种小直径（Auxetic）食管支架和支架移植物的制造。如果使用商业球囊扩张导管进行口腔部署，则最容易实现这种（Auxetic）支架的部署，因为这样就不需要昂贵的专用输送系统。本研究采用了一种新颖的制造途径来开发（Auxetic）薄膜和（Auxetic）食管支架，该途径包括从传统的减法技术到新的加法制造方法。选择聚氨酯作为制造（Auxetic）薄膜和（Auxetic）食管支架的材料，因为它具有良好的生物相容性和非毒性。（Auxetic）薄膜后来用于制造拼接式（Auxetic）食管支架。柔性聚氨酯管状移植物也连接到无缝（Auxetic）食管支架的内腔侧，以防止肿瘤向内生长。使用不同的（Auxetic）标本进行扫描电子显微镜表面形态研究，这些标本是通过不同的传统和新的加法制造技术开发的。对（Auxetic）薄膜进行拉伸测试，以表征其机械性能。对（Auxetic）支架进行支架扩张测试，以分析在球囊导管施加的一系列径向压力下（Auxetic）支架的纵向延伸和径向扩张，并确定（Auxetic）支架失效的压力值。开发了（Auxetic）薄膜和（Auxetic）支架的有限元模型，并将结果与实验结果进行了很好的对比。（Auxetic）聚氨酯薄膜的拉伸测试表明，在不同的单轴拉伸负载值下，样品的泊松比在-0.87 至-0.963 之间。从支架扩张测试中可以发现，（Auxetic）食管支架在球囊导管施加的压力增量范围内（0.5-2.7 巴）从 0.5 毫米径向扩展到 5.73 毫米，并从 0.15 毫米纵向延伸到 1.83 毫米。
